• Energy Research

AbstractThis study conducts a detection and attribution analysis of the observed changes in extreme precipitation during 1951–2015. Observed and CMIP6 multimodel simulated changes in annual maximum daily and consecutive 5‐day precipitation are compared using an optimal fingerprinting technique for different spatial scales from global land, Northern Hemisphere extratropics, tropics, three continental regions (North America and western and eastern Eurasia), and global “dry” and “wet” land areas (as defined by their average extreme precipitation intensities). Results indicate that anthropogenic greenhouse gas influence is robustly detected in the observed intensification of extreme precipitation over the global land and most of the subregions considered, all with clear separation from natural and anthropogenic aerosol forcings. Also, the human‐induced greenhouse gas increases are found to be a dominant contributor to the observed increase in extreme precipitation intensity, which largely follows the increased moisture availability under global warming.

AbstractClimate model projections of extreme precipitation intensity depend heavily on the region: some regions will experience exceptionally strong increases in extreme precipitation intensity, while other regions will experience decreases in extreme precipitation intensity. These regional variations are closely related to regional changes in large‐scale ascent during extreme precipitation events—that is, “extreme ascent”—but the drivers of extreme ascent changes remain poorly understood. Using output from a large ensemble of the Canadian Earth System Model version 2, we show that subtropical changes in extreme ascent likely result from changes in the horizontal scale of ascending anomalies, which are in turn associated with changes in vertical stability. Near the equator, changes in the seasonal mean circulation may be an important factor influencing extreme ascent, but this finding is model dependent.

Abstract Changes in day-to-day (daily) temperature variability have implications for the health of humans and other species and industries such as agriculture. The strongest historical changes in daily temperature variability are decreases in the northern high latitudes annually and in all seasons except summer. Additionally, daily temperature variability has increased in the Northern Hemisphere mid-latitudes during summer and over tropical and Southern Hemisphere land areas. These patterns are projected to continue with additional warming. We conduct a formal detection and attribution analysis, finding the global spatio-temporal changes in daily temperature standard deviation annually and for all seasons except boreal summer are attributable to anthropogenic forcing. Human influence is also detected in some individual 20-degree latitude bands, including the northern high latitudes. Attribution results are generally robust to different methodological choices and this provides confidence in projected changes in daily temperature variability with continued anthropogenic warming.

AbstractWe present the second update to a data set of gridded land‐based temperature and precipitation extremes indices: HadEX3. This consists of 17 temperature and 12 precipitation indices derived from daily, in situ observations and recommended by the World Meteorological Organization (WMO) Expert Team on Climate Change Detection and Indices (ETCCDI). These indices have been calculated at around 7,000 locations for temperature and 17,000 for precipitation. The annual (and monthly) indices have been interpolated on a 1.875°×1.25° longitude‐latitude grid, covering 1901–2018. We show changes in these indices by examining ”global”‐average time series in comparison with previous observational data sets and also estimating the uncertainty resulting from the nonuniform distribution of meteorological stations. Both the short and long time scale behavior of HadEX3 agrees well with existing products. Changes in the temperature indices are widespread and consistent with global‐scale warming. The extremes related to daily minimum temperatures are changing faster than the maximum. Spatial changes in the linear trends of precipitation indices over 1950–2018 are less spatially coherent than those for temperature indices. Globally, there are more heavy precipitation events that are also more intense and contribute a greater fraction to the total. Some of the indices use a reference period for calculating exceedance thresholds. We present a comparison between using 1961–1990 and 1981–2010. The differences between the time series of the temperature indices observed over longer time scales are shown to be the result of the interaction of the reference period with a warming climate. The gridded netCDF files and, where possible, underlying station indices are available from www.metoffice.gov.uk/hadobs/hadex3 and www.climdex.org.